Method of producing steel forging and articles produced thereby



Dec. 4, 1962 w. FADER 3,066,408

METHOD OF PRODUCING STEEL FORGING AND ARTICLES PRODUCED THEREBY 4Sheets-Sheet 1 Filed Dec. 51, 1957 IN VE R WILL/AM L. FAD

By Attorney.

Dec. 4, 1962 w. 1.. FADER 3,066,408

METHOD OF PRODUCING STEEL FORGING AND ARTICLES PRODUCED THEREBY FiledDec. 31, 195'? 4 Sheets-Sheet 2 Dec. 4, 1962 w. FADER 3,066,408

METHOD OF PRODUCING STEEL FORGING AND ARTICLES PRODUCED THEREBY 4Sheets-Sheet 5 Filed Dec. 51, 1957 FILE-.- 1

I/VVENTOR WILLIAM L. FADE/P,

Attorney.

Dec. 4, 1962 w. L. FADER 3,066,403

ME D OF PRODUCING STEEL FORGING ARTICLES PRODUCED THEREBY Filed Dec. 31,195'? 4 Sheets-Sheet 4 lNVE/VTOR W/LL/AM L. FADE/i,

'QOMw OW Attorney.

United States Fatent Office 3,006,403 Patented Dec. 4, 1962 3,066,408METHOD OF PRODUCING STEEL FQRGIN G AND ARTICLES PRODUCED THEREBY WilliamI... Fader, Lorain, Ohio, assignor to United States Steel Qorporation, acorporation of New Jersey Fiied Dec. 31, 1957, Ser. No. 706,377 2Claims. ((31. 29-5523) This invention relates to an improved method ofproducing steel forgings and more particularly to the production ofshell forgings.

In the conventional treatment of billets or slugs to produce shellforgings, the billets are heated to austenitizing temperatures, i.e.well above the upper critical temperature and pierced to form aclosed-end cylindrical body. Immediately thereafter they are hot drawnthrough dies while on a mandrel to reduce the wall thickness to thedesired size. After rough machining of outside surface of forging andbefore heat treatment, the cylindrical body is tapered by a nosingoperation to impart the desired ogive shape thereto. The force requiredfor nosing tends, however, to gather the preheat-treated material of theshell walls in bulges, due to the low column strength, which, afterbeing machined off, reduces the wall thickness below permissible limitsleading to an undesirable percentage of forgings which must be scrapped.

It is accordingly an object of the present invention to providea methodof producing shell forgings which overcomes the foregoing difficulties.

It is a further object of this invention to produce shell forgingshaving improved microstructural characteristics.

The foregoing and further objects will be apparent from the followingspecification when read in conjunction with the attached drawingswherein:

FIGURE 1 is a suitable billet for converting into a shell forging by theprocess of my invention;

FIGURES 2 through 4 are schematic views showing the essential piercing,drawing and nosing steps in the production of shell forgings by myinvention;

FIGURE 5 is a cross-sectional view of the forging after the piercingoperation of FIGURE 2;

FIGURE 6 is a similar view of the forging after the drawing operation ofFIGURE 3;

FIGURE 7 is a cross-material view of the drawn forging of FIGURE 6 afterfinish machining; and

FIGURE 8 is a similar view of the forging after the nosing operation ofFIGURE 4.

Shell forgings are conventionally produced from plain carbon steel tospecified minimum values of 65,000 p.s.i. yield strength, 15% elongationand 30% reduction in area. Steel of the desired composition is cast intoingots which are rolled by conventional processes into roundcorneredsquare billets of the desired diameter and these are cut or broken intolengths or slugs S of suitable size for the production of a single shellforging. Thereafter these slugs are heated to about 2200 F. and piercedby inserting a mandrel 2 therein, while held in a suitable die orcontainer 4. Production of finished forging requires the followingadditional operations.

CONVENTIONAL PROCESS Shells made in this manner of 0.50% carbon steelhave a yield strength of 67,000 to 78,000 pounds per square inch, anultimate strength of 112,000 to 121,000, an elongation of 19% and areduction of area of 50%. When made of 0.40% carbon steel, they average72,515 pounds per square inch yield strength, 119,000 tensile strength,20% elongation, and 48.7% reduction of area.

In the process of my invention, I use steel containing between .35 and65% carbon, .40 to 1.00% manganese, .05 to 30% silicon with normalamounts of phosphorus and sulfur and residual amounts of other elements.Other elements commonly present in low-alloy steels may be used ifdesired. The individual slugs S are heated to a temperature slightlyabove the AC3 temperature to insure complete austenitization withoutexceeding the grain coarsening temperatures and then pierced, as shownin FIGURE 2, at a temperature between the Ar and Ar For the steels ofthis invention, this is a temperature between 1350 and 1600 F. Followingthis the forging is drawn through dies 6 as shown in FIGURE 3, to reducethe wall thickness. If necessary the forging may be reheated betweenpiercing and drawing to insure the proper temperature. The wall of theforging, while within the temperature range of 1350 to 1600 F., shouldbe reduced or deformed an amount sufiicient to produce a change incross-sectional area of between 20 and Following the piercing anddrawing operations, the shell is cooled in still air at least untiltransformation is completed and may thereafter be cooled by anyaccelerated method desired. It is then shot blasted, finished machinedand nosed in a cold forming operation as shown in FIGURE 4.

When so treated, the workpiece has a grain size of ASTM #5 or finer witha peculiar microstructure characterized by a substantial dispersion ofiron manganese carbide and typical fine pearlite, resulting fromsimultaneous working and transformation. 0.50% carbon steel worked intoshells in the manner of my invention had a yield strength of 71,000 to72,500 pounds per square inch, ultimate strength of 111,200 to 111,500,an elongation of 21.5 to 22%, and reduction of area of 51 to 51.4%, whenworked at 1600 F; when forging temperature of 1400 F. was used, tensiletesting of shells showed. average 79,660 yield strength, 112,900 tensilestrength, 23% elongation and 53.7% reduction of area, while working at1350 F. resulted in 74,697 pounds per square inch yield strength,112,073 tensile strength, 18.7% elongation, and 39.4% reduction of area.A 0.40% carbon steel forged at 1450" F. yielded 79,000 to 86,000 poundsper square inch yield strength, 100,000 to 102,000 tensile strength, 20to 21% elongation and 55 to 59% reduction of area.

The resulting mechanical properties are such that there is no need forthe conventional quenching and tempering. In addition, as a result ofthe microstructure, the impact properties and reduction in area areequivalent to or better than those obtained by quenching and tempering.

If desired, workpieces forged in this .manner may be given one or morecold forging passes to obtain surface smoothness and an increase inhardness. The cold working may be performed without the presofteningtreatment frequently required.

According to data obtained the temperature of forging should varysomewhat with the carbon content as follows:

F. 60% carbon 1350 to 1600 50% carbon 1350 to 1600 .40% carbon 1400 to1500 To obtain maximum benefit of the treatment, it is necessary to staywithin these limits. Working at a temperature above the maximums given,results in lowered yield and tensile properties due to recrystallizationof the grains at such temperature. On the other hand, it is necessary 3to stay above the minimum because of lowered ductility. A further pointof considerable interest, namely the transition temperature of shellsmade by the proposed and conventional methods can be illustrated byreference to the following table:

Lower transition temperatures are understood as leading to less brittlesteel at subzero temperatures.

A major advantage of the proposed process-lies in reduced bulgingoccurring during the nosing process. EX- tensive measurements have shownthat my process reduces the bulging observed in forgings produced byconventional operations by about fifteen times and to the extentrendering scrapping from this cause negligible.

From the foregoing, it is seen that forging produced in accordance withthe teachings of my invention readily meet the requirement having ayield strength of at least 65,000 pounds per square inch, an elongationnot less than 15%, a reduction of area of 30%, minimum. Moreover, it isapparent that my process produces such forgings more economically due tothe elimination of a number of steps from the conventional process andthe virtual elimination of scrapping of forgings due to bulging.

While I have shown and described several specific examples of myinvention, it will be understood that these examples are merely for thepurpose of illustration and description and that various other forms maybe devised within the'scope of my invention, as defined in the appendedclaims.

I claim:

1. A method of producing shell forgings without quenching and temperingsaid forgings having a minimum yield strength of 65,000 p.s.i. togetherwith a minimum elongation of 15% and reduction in area of 30%,characterized by a transition temperature below about +30 F. comprisingforming billets of steel containing .35 to .65 carbon, .40 to 1.00%manganese, .05 to 30% silicon and other elements in amounts which do notadversely affect the properties, heating said billets to a temperaturebetween the Ar and Ar temperature of the steel, piercing and drawingsaid billets while at said temperature to form open-end cylindricalforgings, cooling said pierced and drawn forgings to room temperature,finish machining them and cold forming the open end to the desired ogiveshape.

2. A method of producing shell forgings without quenching and tempering,said forgings having a minimum yield strength of 65,000 p.s.i. togetherwith a minimum elongation of 15% and reduction in area of 30%,characterized by a transition temperature below about +30 F., comprisingforming billets of steel containing .35 to .65% carbon, .40 to 1.00%manganese, .05 to .30% silicon and other elements in amounts which donot adversely affect the properties, heating said billets to a.temperature between 1350 and 1600 F. for steels having about .50 to .60%carbon and between 1400 and 1500 F. for steels having about .40% carbon,piercing said billets while at said temperature to form open-endcylindrical forgings, drawing said forgings while in said temperaturerange to reduce the cross-sectional area between 20 and cooling saidpierced and drawn forgings to room temperature, finish machining themand cold forming the open end to the desired ogive shape.

References Cited in the file of this patent UNITED STATES PATENTS1,437,690 Sylvester Dec. 5, 1922 1,598,240 Carlson Aug. 31, 19261,925,823 Singer Sept. 5, 1933 1,941,101 Meyer Dec. 26, 1933 1,946,117Sparks Feb. 6, 1934 2,183,637 Biginelli Dec. 19, 1939 2,569,248 MillerSept. 25, 1951 FOREIGN PATENTS 120,799 Great Britain Nov. 28, 1918

1. A METHOD OF PRODUCING SHELL FORGINGS WITHOUT QUENCHING AND TEMPERINGSAID FORGINGS HAVING A MINIMUM YIELD STRENGTH OF 65,000 P.S.I. TOGETHERWITH A MINIMUM ELONGATION OF 15% AND REDUCTION IN AREA OF 30%,CHARACTERIZED BY A TRANSITION TEMPERATURE BELOW ABOUT -30*F.